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What happened to the dog according to the gardener？
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Glass is everywhere in our lives. It is so common 【21】______ we hardly think about it. We 【22】______ it when we look out of the window and if we wear glasses. We drink from it and sometimes eat from it. The light in our homes comes through glass windows in the daytime and from glass lights 【23】______ . Glass 【24】______ in homes, schools, businesses, industry, and automobiles.
Fortunately for us, glass is 【25】______ very inexpensive materials. The main material is sand from quartz rock. The mixture is heated until it becomes a syrupy 【26】______ . When the liquid cools, it becomes glass.
No one knows 【27】______ first discovered glass or how. Early humans used obsidian, a natural glass 【28】______ by volcanoes, to make tools and jewelry. People probably began making glass themselves around 3000 B.C. in Syria. Then in a war 【29】______ Egypt and Syria in 1400 B. C., Syria became part of Egypt. The Egyptians took Syrian glassmakers 【30】______ to Egypt, and over the centuries the entire eastern Mediterranean area became a glassmaking center.
Probably around 300 B.C. the blowpipe 【31】______ . Egyptian glassmakers developed the use of the blowpipe. They specialized 【32】______ beautiful jewelry, dishes, and other containers.
The Romans soon started making their own glass. Then they 【33】______ that glass could be used to make windows. 【34】______ centuries later, Europeans made magnificent church windows 【35】______ colored glass.
【36】______ 1900 companies have developed many new types of glass. Safety glass is a sandwich of glass and plastic. If it breaks, the pieces stay together 【37】______ flying in all directions. This invention is very useful 【38】______ automobile windows.
Today most glass is made 【39】______ machines in large factories. No one 【40】______ it. People use television and computers to control the machines.
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